Processes for an improvement to gasoline octane for long chain paraffin feed streams

ABSTRACT

Methods for making higher-octane fuel components from a feed stream of C8+ paraffins, including catalytically cracking the C8+ paraffins using a Zeolite catalyst to produce a reaction product of mid-chain paraffins and olefins and short-chain paraffins and olefins. The reaction product comprises liquid phase paraffins having an increased Octane Value over the feed stream paraffins. The reaction product further comprises a gas phase of short-chain paraffins which are separated from the liquid phase. In embodiments, the short chain olefins are hydrogenated to form mid-chain paraffins and a gas phase containing short-chain paraffins.

FIELD

Disclosed is a low-severity, catalytic reaction process appliedselectively to long-chain paraffinic compounds, particularlyn-paraffins, such as those present in traditional, catalytic reformingprocesses. The low-severity process, operated with or without hydrogen,converts targeted long-chain paraffins to higher-octane compounds idealfor gasoline blending, along with a byproduct of mixed light gases.

BACKGROUND

Global demand for high-octane gasoline blendstocks continues to grow tosupport new higher-compression internal combustion engines. The presenceof long-chain paraffin compounds (“LCPs”), particularly n-paraffins, inpetroleum products output from traditional catalytic reformers,typically lowers the octane value of the aromatic-rich blendstocksproduced for the octane pool. These LCP compounds are subsequentlyblended into the gasoline pool and thereby reduce octane levels,resulting in lower fuel efficiency for spark-ignited combustion engines.

The Octane Value of a gasoline fuel component is an important factor toresist engine knocking in high-compression piston engines. Octane iscalculated, for example, as motor octane number (MON) or research octanenumber (RON). As used herein, the term “Octane Value” is defined as theaverage (MON+RON)/2.

In a typical petroleum refinery, high-octane gasoline blendstock that isoutput from the catalytic reforming process, or from fluid catalyticcrackers, is sent straight to the gasoline blending pool. However, suchunits as catalytic reformers may fail to process long-chain paraffinseffectively, as that would require operating the reformers understressful conditions, which can result in heavy volume loss (i.e. 5%-30%), and in many cases excessive coking and/or shortened life of thecatalyst. The result is an excess amount of lower-octane, long-chainparaffin in the reformate. The presence of a large portion of theseundesirable paraffin constituents—C₈ and higher long-chain paraffins—canneedlessly lower the octane value of the entire gasoline pool.

Traditional catalytic naphtha reforming is operated at high reactortemperature, ca. 500° C., and pressures up to 340 psi, which favorformation of aromatic gasoline range hydrocarbons. Unlike catalyticreforming, the present invention is operated at lower temperatures andlower pressures, which favor paraffin cracking without aromaticsaturation.

Also, in a typical refinery, naphtha-hydrotreating is a precursor tocatalytic reforming and is designed to eliminate sulfur that coulddamage the reformer catalyst. However, naphtha-hydrotreating results inincreased paraffin levels. Reformate feed streams therefore typicallycontain an undesirable amount of low-octane, long-chain paraffins in theC8+ range which are suitable for utilizing this invention.

Transforming long-chain paraffins to high-octane blendstocks is achallenge for the catalytic reformer. To increase octane, catalyticreformers typically must increase operating severity, which results inhigher energy costs and lower liquid volume yields. Increasing severityalso results in coking and/or shorter catalyst life cycles, particularlyimpacting semi-regenerative reformers. Refiners are thus challenged tomaximize liquid yields, lower costs and sustain catalyst life.

This invention is also unlike traditional gasoil hydrocracking whichsaturates poly-aromatic compounds and cracks C16 to C44+ paraffincompounds to diesel and jet fuel. Gasoil hydrocracking is operated athigh pressures and 300-475° C. and very high pressures (typically 500 to3000 psi) to favor saturation of poly-aromatic compounds, the removal ofsulfur and the cracking of larger high-molecular-weight paraffins. As aresult, the gasoil hydrocracking process reduces the aromatic contentwhile creating lighter paraffin compounds in the diesel fuel boilingrange. In such a process, significant quantities of aromatics presentafter gasoil hydrocracking are considered undesirable. Also, gasoilhydrocracking catalysts may contain platinum (Pt) or palladium (Pd), oralternatively Molybdenum (Mo) sulfide promoted by nickel (Ni) or cobalt(Co). Because of the large size of gasoil molecules, larger porezeolites are generally used in gasoil hydrocracking. Unlike gasoilhydrocracking, this invention uses smaller pore, less harsh zeolitecatalysts operating at far lower severity levels resulting in nosaturation of aromatic compounds.

Raising the final octane number of gasoline components would add valueto the overall gasoline pool. The octane values of heavier paraffincomponents are generally much lower than those of aromatic compounds incatalytic reforming effluent (reformate), and therefore tend to dragdown the overall octane value of reformate by 1 to 10 octane numbersusing the ((R+M)/2) method. A key factor in increasing the Octane Valueis reducing the proportion of higher-boiling, heavy paraffins,particularly n-paraffins. These higher boiling paraffins impose anoctane “Drag Factor” on the gasoline blend. The term “Octane DragFactor” refers to the comparison of the Octane Value of a given paraffinas compared to the Octane Value of 87. Thus, Octane Drag Factor=OctaneValue−87. FIG. 1 presents the Octane Drag Factor for various n-paraffinsand iso-paraffins.

Table 1 demonstrates the significance of the average Octane Drag Factorby carbon number for higher-boiling n-paraffins and iso-paraffinstypical of reformate samples.

TABLE 1 Paraffin in Typical Octane Reformate Boiling (R = M)/2 SamplesRange Drag Factor C6 Paraffins  50-69° C. −11 C7 Paraffins  80-99° C.−23 C8 Paraffins  99-125° C. −33 C9 Paraffins 125-151° C. −35 C10Paraffins 152-183° C. −57 C11 Paraffins 183-190° C. −124 C12 Paraffins190-216° C. −176 C13 Paraffins 216-235° C. −178

The effect of different n-paraffins on Octane Value by carbon number ina typical refinery LCP product stream is demonstrated in Table 2.

TABLE 2 n-Paraffin Impact on RON and MON Typical Reformate Feed:n-Paraffin Content C# Compound Typical Wt % RON MON 4 n-Butane 0.2 113114 5 n-Pentane 1.0 62 66 6 n-Hexane 2.1 19 22 7 n-Heptane 10.5 0 0 8n-Octane 6.8 −18 −16 9 n-Nonane 2.5 −18 −20 10 n-Decane 0.7 −41 −38 11n-Undecane 0.2 −65 −64 12 n-Dodecane 0.7 −88 −90 13 n-Tridecane 0.1 −89−93 Total n-Paraffin 24.8 — — C8+ n-Parafinn 11.0 — —

As shown in FIG. 2, increasing levels from 0 to 10% of C₉₊ heavyparaffins, particularly n-paraffins, in a reformate stream reducesOctane Values from 104.3 down to 96.2 octane.

This demonstrates that even a small percentage of C8+long-chain-paraffin constituents, particularly n-paraffins, cansubstantially hinder octane values in gasoline blendstocks.

SUMMARY

In one aspect, referred to herein generally as Increase to Fuel Economy,or the “I2FE Process”, feed containing C₈₊ paraffins is processed toselectively convert low-octane, long-chain paraffins into shorter chainparaffins by chemical reaction, with or without added hydrogen. The I2FEProcess provides an increase in the octane level with high energydensity compounds of the liquid yield for use as high-octane gasolineblendstocks. The short-chain paraffins reduce the octane dragparticularly of n-paraffins impacting the blended Octane Value of theliquid yield. This process also produces a clean byproduct of mixedlight C₁ to C₅ hydrocarbon gases and liquids (upon cooling) for reuse infuels.

An object of the I2FE Process is to increase the octane of a basefeedstock by eliminating low-octane constituents which are transformedto higher value products with minimal yield loss.

Another object of the I2FE Process is to increase the octane rating ofgasoline blendstocks. In a particular aspect, it is an object to upgradethe octane performance of petroleum reformate used in blending premiumgasoline, while producing a byproduct of sulfur-free C₁₊ light gases.

A further object is to provide a process useful in a refinery, typicallydownstream of naphtha reforming, to selectively crack long-chainparaffin compounds, particularly n-paraffins while preserving thehigh-octane aromatic molecules.

The I2FE Process advantageously allows the tailored separation andprocessing of the reformate by means of slit stream, distillation and/orother separation methods to selectively treat the paraffin compoundshaving the highest drag factor on the overall Octane Value, therebyincreasing the octane value of the effluent with minimal loss.

The process is tailored based upon the characteristics of typicalaromatic-rich feed streams with LCP's and the selective targeting ofparaffinic compounds to be transformed to high-octane constituents toincrease octane and limit volume loss.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram comparing Octane Drag Factor for various C8 to C12n-paraffins and iso-paraffins typical in reformate.

FIG. 2 is a diagram showing the impact of n-Paraffins (% wt.) onreformate Octane Value.

FIG. 3 is a process flow diagram showing a Cracking System processincluding on-purpose hydrogen.

FIG. 4 is a diagram showing compositions of the pre-reaction,post-reaction, and post-flash feed streams.

FIG. 5 is a diagram of an I2FE process without hydrogen.

FIG. 6 is a diagram showing a second exemplary I2FE process whichincludes a hydrogen feed to the cracking chamber.

FIG. 7 is a graph showing that aromatics in the feed stream werepreserved to a substantial extent using the ZSM-5 catalyst.

FIG. 8 is a graph showing benzene reduction in comparison to I2FEreactor temperature.

DESCRIPTION

For the purpose of promoting an understanding of the principles of theinvention, reference will now be made to the embodiments illustratedherein and specific language will be used to describe the same. It willnevertheless be understood that no limitation of the scope of theinvention is thereby intended. Any alterations and further modificationsin the described embodiments, and any further applications of theprinciples of the invention as described herein are contemplated aswould normally occur to one skilled in the art to which the inventionrelates. Embodiments of the invention are shown in detail, but it willbe apparent to those skilled in the relevant art that some features thatare not relevant to the present invention may not be shown for the sakeof clarity.

The I2FE Process is a unique process for the treatment of base feedstockcontaining higher-boiling paraffins to increase overall Octane Value.The low severity cracking process provides for targeting of long-chainparaffins without a significant effect on other components, e.g.,aromatics.

In refining, the I2FE Process differs significantly from catalyticnaphtha reforming. The typical catalytic reformer is configured toincrease the aromatic content of a naphtha stream by (a) dehydrogenationof cycloalkanes, and (b) cyclization of C₆+ alkyl chains followed bydehydrogenation. The cyclization/dehydrogenation step has the slowestrate of reaction, and therefore full conversion of paraffins toaromatics is notably incomplete in reforming. Some broad-spectrumcracking does occur as a result of using harsh reforming catalystsoperating at high severity levels, however this can result inundesirable high yield losses (i.e. 5-30%) with no specific impact onthe low-octane compounds. Heavy paraffins present in the catalyticreformer effluent (reformate), and in some cat-cracked gasoline, havevery low octane, and removal of small amounts of these can significantlyincrease the octane of the gasoline blendstock.

Overview

The I2FE Processes increase Octane Value by converting long-chainparaffins into shorter chain, higher octane paraffins or a combinationof high-octane paraffins and olefins. A primary focus is the treatmentof n-paraffins based on the proportion and Octane Values of thosecomponents.

As an overall process, the conversion of paraffins may be represented bythe following three steps:

C_((x))H_((2x+2))(paraffin)→C_((y))H_((2y+2))(paraffin)+C_((z))H_((2z))(olefin)

C_((x))H_((2x+2))(n-paraffin)→C_((y))H_((2y+2))(n-paraffin)+C_((z))H_((2z))(n-olefin)

C_((z))H_((2z))(olefin)+H₂→+C_((z))H_((2z+2))(paraffin)

where x=y+z. In the first two steps, the C8+ paraffins, includingparticularly the n-paraffins are converted into combinations of shorterparaffins (e.g., n-paraffins) and lower carbon olefins (e.g., C5paraffin+C3 olefin, C6+C2, etc.). In the third step, if hydrogen ispresent, the lower carbon olefins are hydrogenated to form thecorresponding paraffins, e.g., n-paraffins.

The I2FE Process includes the treatment of long-chain paraffins. As usedherein, a “long-chain paraffin”, or “LCP”, is a paraffin containing 8 ormore carbons. In an embodiment, the LCPs contain from 8 to 13 carbons,and are referred to herein as C8-13 LCPs. LCPs may include n-paraffins,iso-paraffins and cyclo-paraffins. In another embodiment, the LCPs arenon-cyclic, and in another aspect the LCPs are normal, straight-chainn-paraffins having from 8 to 13 carbon atoms. An “LCP Feed” is a feedstream that includes long-chain paraffins. For example, a C₈-C₁₃ LCPFeed is a feed stream that contains paraffins including 8-13 carbons. Inan embodiment, the disclosed processes specifically target the crackingof n-paraffins, namely, n-octane, n-nonane, n-decane, n-undecane,n-dodecane and n-tridecane, as these have the most undesirable octaneratings in the feed (e.g. reformate) that negatively impact the octanevalue of the gasoline blendstocks.

It will be appreciated that the LCP Feed may include other components.For example, a C₈-C₁₃ LCP Feed may include many other paraffins, such as2-methylheptane, an isomer of n-octane, and cyclooctane, acyclo-paraffin. An LCP Feed may also include other types of hydrocarbonssuch as aromatics and olefins. In an aspect, the paraffins designated asbeing in an LCP Feed comprise at least 10 wt % of the LCP Feed, morepreferably at least 25 wt %, and most preferably at least 40 wt %. Forpurposes herein, all percentages are wt % unless indicated otherwise.

By way of example, in the absence of hydrogen, the n-paraffin C₈H₁₈ maybe converted to C₆H₁₄ (hexane) and C₂H₄ (ethylene). In an alternativeexample, the C₈H₁₈ may instead be converted to C₅H₁₂ (pentane) and C₃H₆(propylene). It is also possible that paraffins formed in the reactionmay be subsequently converted to even shorter paraffins and olefins. Inthe presence of hydrogen and a metal-acid catalyst in these examples,olefins produced from the reaction are largely converted to paraffins.

It will be appreciated that a similar reaction scheme applies fornon-normal paraffins, e.g., iso-paraffins. That is, for example, highercarbon iso-paraffins may be converted to lower carbon olefins andparaffins. In the presence of hydrogen and a metal-acid catalyst, thelower carbon olefins are converted to the corresponding paraffins. TheAverage Octane Value for C8+ non-normal paraffins is ˜70 Octane, whilethe average Octane Value for C8+ n-paraffins is below −20 Octane.Cracking both types of paraffins will make the Octane Value go higher.Thus, while the primary focus of the I2FE process is directed to theconversion of n-paraffins, it will be appreciated that iso-paraffinsthat are present may be similarly converted.

The disclosed processes selectively transform long-chain paraffins toincrease the overall Octane Value of the blendstock. Therefore, in anaspect, disclosure herein of the treatment of the n-paraffins alsoincludes treatment of other paraffins, e.g., iso-paraffins, that arealso present. The mid-chain C4-C6 paraffins are of somewhat lesserimportance to cracking as they typically have lower volumes with a moreacceptable octane rating. In general, the disclosed processes produce aC5+ liquid product with an increased Octane Value over the feed streamto the process. Embodiments may provide increases of Octane Value by atleast 1 unit, preferably at least 5 units, above the feed stream OctaneValue.

The I2FE Process can be tailored under a wide variety of scenarios toselectively crack long-chain, paraffin compounds, particularlyn-paraffins, at low temperatures and low pressures resulting in improvedyields of high-octane gasoline blendstocks. The processes can be appliedto a wide variety of long-chain, paraffin feeds. For example, the I2FEProcess is useful downstream of various existing process streams in arefinery. In preferred embodiments, the I2FE Processes can beeffectively applied to output streams downstream of a catalytic reformer(reformate) or a catalytic cracker (cat-cracked gasoline) as a precursorto the gasoline blending process. The composition of the I2FE feedstream determines the spectrum of compounds to be processed, thesuitable operating conditions of the process, and the choice of catalystfor the reaction.

As one example, a refinery reformate with 30% total paraffin content(including straight-chain and branched chain paraffins) was transformedin accordance with the present disclosure. As shown in Table 3, thereformate had a 5.5 Octane Value increase with byproducts of clean lighthydrocarbon gases:

TABLE 3 Octane Increase RON MON (R + M)/2 Reformate Input 95.8 85 90.4Product Effluent 101.3 90.5 95.9

In another example, a reformate feed having an n-paraffin profile asshown in Table 4 was treated using the I2FE Process. Table 4 shows inthe column “Standard I2FE Feed” the n-paraffin content of a reformatefeed stream comprising 11.36 wt % n-paraffins in the C4-C12 range. Then-paraffins underwent a variety of changing operating conditions (at250, 270, 300° C.) and the results show how the n-paraffin compoundswere reduced, up to 58 wt %, from the I2FE catalytic reaction. Further,the composition of the n-paraffins showed a substantial shift fromC4-C12 to C3-C9 range of compounds.

TABLE 4 Weight % of n-paraffin compounds Stan- dard 12FE 12FE I2FE %Delta I2FE Effluent Effluent Effluent 300° C. Compound C# Feed (250° C.)(270° C.) (300° C.) vs. Feed Methane 1 0.00 0.00 0.00 0.00 — Ethane 20.00 0.00 0.00 0.00 — Propane 3 0.00 0.02 0.10 0.19 — N-Butane 4 0.200.10 0.33 0.49 149% N-Pentane 5 0.21 0.24 0.57 0.66 214% N-Hexane 6 0.170.25 0.42 0.39 133% N-Heptane 7 4.78 4.33 3.43 2.11 −56% N-Octane 8 3.152.82 1.65 0.76 −76% N-Nonane 9 1.92 1.40 0.42 0.13 −93% N-Decane 10 0.730.31 0.04 0.00 −100%  N-Undecane 11 0.16 0.00 0.00 0.00 −100% N-Dodecane 12 0.03 0.01 0.02 0.01 −57% TOTAL n- 11.36 9.49 6.97 4.75−58% Paraffins

As a result of the I2FE cracking, the n-paraffins were reduced from 11.4wt % in the feed to 4.8 wt % in the liquid effluent. The iso- andcyclo-paraffins and olefins were reduced by 2 wt %, and the aromaticsincreased to 67 wt % of the total I2FE liquid effluent, compared to 58wt % of the reformate feed.

Table 5 depicts the same n-paraffin compounds of Table 4 pre- andpost-I2FE reaction but applying the (R+M)/2 Octane Value to demonstratethe octane×weight % index factor that results from the reduction inn-paraffins. As shown in Table 5, the octane×weight % of the n-paraffinrange moved from −93 for the feed stream to as high as +89 as a resultof the I2FE process. On a weighted average basis, the Octane Valueshifted from −8 up to +19, a 27-point increase largely attributable tothe reduction in the low-octane, long-chain n-paraffin compounds.

TABLE 5 n-Paraffin Octane × Weight % Pre-I2FE Post-I2FE Post-I2FEPost-I2FE Compound (R + M)/2 Feed 250° C. 270° C. 300° C. Methane EthanePropane N-Butane 114 22.4 11.8 37.7 55.7 N-Pentane 64 13.5 15.5 36.642.5 N-Hexane 21 3.4 5.1 8.7 7.9 N-Heptane 0 0.0 0.0 0.0 0.0 N-Octane−17 −53.6 −47.9 −28.0 −12.9 N-Nonane −19 −36.5 −26.6 −7.9 −2.5 N-Decane−40 −28.9 −12.4 −1.4 0.0 N-Undecane −64 −10.3 0.0 0.0 0.0 N-Dodecane −89−2.9 −1.3 −1.4 −1.3 Σ (Octane × Wt %) −92.9 −55.7 44.2 89.4 Σ(Octanex Wt%)/Σ Wt −8.2 −5.9 6.4 19.6 % (Avg)

Table 6 depicts the total compositional impact of the I2FE process onthe entire reformate feedstream for the above illustration. The I2FEProcess was targeted on reducing the low-octane n-paraffin compounds.Side reactions did have a small impact on other aliphatic compounds(iso-paraffins, cycloparaffins and olefins) resulting in a net 1.9%decrease in concentration of these compounds. The aromatic content ofthe I2FE liquid effluent increased its concentration up to 14%, a highlydesirable result since reformate is the primary source of aromatics ingasoline. In total, the Octane Values (using (R+M/2) method) of the I2FEeffluent versus the reformate feedstream increased by up to 8.2 in thisexample. This result is largely attributed to the 58% wt. reduction inhigher n-paraffins in the I2FE effluent.

TABLE 6 % Delta I2FE I2FE I2FE 300° C. Compound Reformate EffluentEffluent Effluent vs. Type Feed (250° C.) (270° C.) (300° C.) Feedn-Paraffins 11.36 9.49 6.97 4.75 −58% Iso-Paraffins 24.21 23.57 23.4222.35 −8% Naphthalenes 4.02 3.84 4.20 4.44 10% Aromatics 58.34 61.1363.52 66.77 14% Olefins 1.33 0.99 1.08 0.88 −34% — 0.74 0.97 0.80 0.8211% TOTAL 100.00 100.00 100.00 100.00 0%

I2FE System

A study was conducted to exemplify the extent of paraffin cracking andrecovery in a simulated system based on real reaction data. A feedstockof 70,000,000 gallons of reformate per year was simulated with afour-unit operation to determine heat exchange and capital cost. Thechemical compositions for the reformate feed (“REF”) and the outlet ofthe small-scale reactor were utilized as the input for the refinerysimulation. A process flow diagram is shown in FIG. 3 includingon-purpose hydrogen.

The reformate feed is combined with the high-pressure hydrogen feed andthe resulting cold feed is moved into a preheater for the reactor. Theresulting hot feed enters the cracking reactor where the paraffins arecracked over a suitable catalyst, e.g., a zeolite/molybdenum catalyst.The reaction conditions are set at 365° C. and 100 psi with a spacevelocity of 1.5 WHSV. The hot effluent is then cooled to 35° C. The coldeffluent enters an isothermal flash drum and light gases (i.e. H₂,paraffins, olefins) are off gassed from the liquid product steam. As analternative, the cooler could be designed as a preheater for thereactor.

The compositions of the pre-reaction, post-reaction, and post-flash feedstreams are shown in FIG. 4.

The composition notably changes in the Reactor where long-chainn-paraffins are cracked into shorter, higher octane, paraffins. Totalparaffin content remains relatively consistent, in part because crackingof paraffins only leads to lighter paraffins. Long-chain paraffincontent in the product stream lowers from 19.9% feedstock content to10.8%, and in turn the middle chain content increases by 27%. Thedecrease in long-chain paraffin composition only amounts to about a 5%loss in mass after flash distillation. This 5% loss in mass isequivalent to a 2% loss in volume for this system.

Table 7 provides more specific data for this system. As shown, theamount of C7+ paraffins in the product decreased by approximately halfthe amount of long-chain paraffins in the reformate feed. Themiddle-chain paraffins increased 27%.

TABLE 7 Simulation Data with On-Purpose Hydrogen HOT HOT Lb/hr REFHYDROGEN FEED EFFLUENT PRODUCT OFFGAS Hydrogen 0 506 506 6 0 6 Paraffin22455.9 0 22455.9 22918.0 20113.2 2804.8 Middle Chain Paraffin 11103.5 011103.5 16893.3 14166.2 2727.1 Long Chain Paraffin (C7+) 11261.9 011261.9 5876.4 5828.2 48.2 Alkene 90.5 0 90.5 148.3 118.8 29.5Naphthenes 1267.0 0 1267.0 639.0 628.4 10.6 Benzene 1515.9 0 1515.92002.5 1969.8 32.8 Toluene 7653.1 0 7653.1 8974.4 8931.8 42.5 Xylenes9186.0 0 9186.0 9984.2 9970.2 14.0 Trimethylbenzenes 3908.6 0 3908.64090.7 4089.1 1.6 Misc. Alkyl Benzenes 10577.5 0 10577.5 8455.2 8450.94.2 Total 56563.9 506 57069.9 57069.9 54153.4 2916.5 GPM 146 142.6

Catalytic Paraffin Cracking

The basic I2FE cracking process proceeds as shown in FIG. 5. The processinvolves the use of a suitable long-chain paraffin feed (“LCP Feed”) tothe low-severity, paraffin cracking chamber. The cracking chamber isconfigured to convert the LCPs preferably to middle-chain paraffins. Asused herein, a “middle-chain paraffin”, or “MCP”, is a paraffin that has5 to 7 carbon atoms. MCPs are liquid at room temperature and arecontained in the liquid product phase. The MCPs have Octane Values thatare higher than the LCPs, thus resulting in a paraffin product thatcollectively has a higher Octane Value than the paraffin components ofthe LCP Feed.

As a result of the cracking of the LCP there will be an amount ofshort-chain paraffins formed. As used herein, a “short chain paraffin”,or “SCP”, is a paraffin having 4 or fewer carbons. These SCPs are gasesat room temperature and are contained in the gaseous product phase.

The cracking of the LCPs may also result in the production of otherLCPs, which are shorter than the LCPs from which they are derived, butwhich are not as short as MCPs. For example, C₁₃ may be cracked to formC₅ n-paraffin (pentane) and C₈ n-paraffin. As C₅ n-paraffin is an MCP,and C₈ n-paraffin is an LCP, they each have an Octane Value that ishigher than that of the C₁₃ n-paraffin. They also may have morefavorable physical properties, such as viscosity, lower freeze point andfewer carbon-forming deposits, as compared to the original LCPs.

As noted, the resulting product mix includes both a liquid phase and agas phase. The liquid phase comprises a C5+ paraffin mixture includingfeedstock components and paraffins resulting from the I2FE crackingprocess. The gas phase comprises n-paraffins having 4 or fewer carbons,as well as potentially hydrogen and other light gases. As describedherein, the C5+ paraffin mixture has an Octane Value in excess of thatof the feed stream, typically by 5 or more units. The liquid productthereby represents a fuel blending component having an advantageouslyincreased Octane Value. The C4− gases are separated from the liquidphase product and are available for other uses.

The catalytic paraffin cracking reaction has little impact on aromaticsin the LCP Feed. The impact of the transformation is the selectiveconversion of heavier n-paraffin components. The transformed feed streamthen undergoes a simple separation process to remove excess hydrogenfrom the effluent to be recycled. The liquid stream exits the processwith an upgraded octane at high yield.

Hydrogen Consumption

The I2FE cracking process consumes an amount of hydrogen if processedwith a metal-acid catalyst. The consumption of H₂ is sufficiently lowthat the I2FE Process may, for a given LCP Feed, be converted withoutsupplemental H₂.

Each n-paraffin undergoes a series of cracking reactions that result inthe formation of two (or more) smaller paraffins and consumes onemolecule of hydrogen. For example:

C₁₀H₂₂+H₂→C₄H₁₀+C₆H₁₄

Therefore, the moles of hydrogen consumed are equivalent to the increasein moles of paraffin.

In a series of experiments, hydrogen consumption rates were calculatedfor 65,000 pounds of standard reformate. From the GC data gathered, wt %is interpreted as grams compound per 100 grams total. Using themolecular weight of each component, moles/100 g is calculated, which isthen converted to moles/kg. For a typical reformate sample this gives atotal amount of n-paraffin of 9.138 moles/kg. After reaction at 300° C.,the product has a total of 10.129 moles/kg of n-paraffin, an increase of0.991 mol/kg. This increase is largely due to hydrocracking. Since theincrease in moles of hydrocarbon product is equivalent to moles ofhydrogen consumed, 0.991 moles H2/kg reformate was consumed. Convertingmoles of H₂ to mass, then everything to pounds, gives a hydrogenconsumption rate of 0.002 lb/lb reformate. A feed of 65,000 lb/h wouldtherefore consume 130 lb H2/h.

In one embodiment the LCP Feed does not need to contain on-purposehydrogen to support cracking in the I2FE Process. While hydrogen mayseparately be useful to limit catalyst coking, surplus hydrogen may bescarce, so the I2FE process allows added functionality by the use ofdual or multi-bed reactors (fixed, moving or fluid beds) operating in afashion to allow continuous regeneration of the catalyst. A furtheralternative is the use of a single automatically regenerative catalystwith a single-bed reactor.

On-Purpose Hydrogen

Referring to FIG. 6, there is shown a second exemplary I2FE Processwhich includes a hydrogen feed to the cracking chamber. The LCP Feed,e.g., “Reformate Feed”, is provided to a reaction chamber where thelow-severity paraffin cracking of the long-chain n-paraffins occurs. Thesupplemental hydrogen feed is available for cracking of the long-chainn-paraffins, and hydrogenation of the alkenes produced during thesereactions. The hydrogen feed also contributes to reducing coking of thecatalyst and may participate in hydrodealkylation of C2+ alkyl benzenesand hydrogenation of olefins in the feed stream.

Reformate Feed Stream

Petroleum reformate—the liquid effluent of the catalytic reformer—is agasoline blendstock which can have a wide range of hydrocarboncomponents depending upon the operating conditions of the reformer.Reformate typically has a significant proportion of long-chainn-paraffins, particularly C8-13 n-paraffins. The presence of thelong-chain n-paraffins causes an octane drag on the reformate. The lowoctane, long chain n-paraffins are the compounds targeted fortransformation using the I2FE Process.

The I2FE Processes in a refinery may be desirably positioned downstreamof the naphtha reformer. The preferred feedstock for the I2FE Process isa long-chain paraffin effluent from the reformer which has already beendesulfurized. Depending on the feedstock source, the reformate feedstockcan be processed without other special pre-treatments and can operatewith or without on-purpose hydrogen. Some refiners have spare hydrogenavailable, in which case the use of hydrogen may be preferred as a meansto reduce coking of the catalyst, if used in conjunction with ametal-impregnated catalyst. However, operation of the I2FE processwithout hydrogen does reduce the amount of benzene produced, which ishighly advantageous for gasoline blendstocks. The process can operateusing the entire effluent reformate stream, using operating conditionsto selectively crack the C8+ n-paraffin fractions.

Reformate Compositions

The following Table 8 depicts the typical components of petroleumreformate as exemplified by 5 reformate samples taken from US refineriesusing the GC method (ASTM D6833). Refineries will have differingresults, subject to ever-changing conditions and geography, but thisdata serves as a range of representative examples.

TABLE 8 Reformate Compositions Weight % Compounds in Sam- Sam- Sam- Sam-Sam- Reformate ple 1 ple 2 ple 3 ple 4 ple 5 AVERAGE Total Paraffins42.08 15.62 30.59 24.49 29.35 28.43 Total Naphthenes 2.13 0.33 0.93 1.142.56 1.42 Total Olefins 0.17 0.18 0.26 0.09 1.40 0.42 Total Aromatics55.64 83.87 68.23 74.27 66.69 69.74

These reformate samples had a variety of C6+ n-paraffin compounds asdepicted below in Table 9. On average, the very-low-octane n-paraffins(C8 and above) comprised 7 to 14 wt % long-chain n-paraffins, for anaverage of over 10 wt %.

TABLE 9 C6-C13 n-Paraffin Components Weight % Sam- Sam- Sam- Sam- Sam-Compound ple 1 ple 2 ple 3 ple 4 ple 5 AVERAGE C6 N-Paraffins 6.34 0.003.88 0.00 0.10 2.06 C7 N-Paraffins 12.80 2.92 14.23 11.36 11.28 10.52 C8N-Paraffins 6.88 6.57 5.74 7.22 7.68 6.82 C9 N-Paraffins 1.95 2.84 1.182.76 3.68 2.48 C10 N-Paraffins 0.33 0.81 0.02 0.80 1.47 0.69 C11N-Paraffins 0.13 0.29 0.06 0.22 0.41 0.22 C12 N-Paraffins 0.83 0.64 0.340.64 0.84 0.66 C13 N-Paraffins 0.05 0.07 0.00 0.30 0.23 0.13

Reduced Severity Reformate

Reformate is often processed sub-optimally, due to operating constraintswithin the reformer operation. However, the I2FE Processes can generatemore octane-barrels (Octane Value×liquid volume yield) if the severityof the upstream reformer operation is reduced. This impacts thecharacteristics of the reformate and the target octane requirements forgasoline blending. Lowering the severity of the reformer provides moreliquid volume of lower-octane reformate feedstock for the I2FE Processto convert to higher-octane gasoline blendstock.

In one configuration, the catalytic reformer severity is reduced toincrease reformate yield of 5% to 15%, with the reformate having a lowerOctane Value, but higher paraffin content. This modified reformatecomposition is then processed using the novel I2FE Processes, resultingin increased overall yields and higher octane than achievable from thecurrent catalytic reformer process alone. This also helps extend thecatalyst life of the catalytic reformer (prone to coking at highseverity levels) and improve refinery economics for blending high-octanegasoline.

Cat-Cracked Gasoline Feed Stream

As another example of a feed stream, the I2FE Processes are utilized toprocess Cat-Cracked Gasoline (CCG) containing long-chain paraffins,although effluent from Cat-Cracked Gasoline is less optimal as feedstockdepending on the amounts and types of long-chain paraffins present andother considerations. In one embodiment, a variety of cat-cracked-napthacompounds, output from the catalytic cracking operation, are furtherprocessed downstream using the methods disclosed herein. A typicalcat-cracked feedstock contains the following compounds listed in Table10 by wt %:

TABLE 10 Sample Cat-Cracked Feed Stream Paraffins ≤C7 27.8 Paraffins ≥C816.3 Naphthenes ≤C7 5.8 Naphthenes ≥C8 3.2 Olefins ≤C7 17.7 Olefins ≥C82.8 Aromatics 24.8 Unknown 1.6 TOTAL 100.0

CCG also typically has a higher concentration of olefins (alkenes) andlower amounts of aromatics compared to the catalytic reformer feed. Itis preferred to separate the light CCG stream from the heavier C8+CCGstream which have lower octane values and only use the heavy stream forthe I2FE process. This is to avoid harming the octane value of less thanC8 olefins. It is an option to hydrotreat the heavy C8+ stream prior toI2FE processing, which would remove sulfur and increase paraffin contentsomewhat. Any C8+ olefins processed through the I2FE reactor andsaturated by the addition of hydrogen, typically produce shorter-chainparaffins. These C8 to C13 olefins are cracked to regain octane from MCPand olefin products and to provide C2, C3 and C4 off-gases asbyproducts.

Feedstock Preprocessing

A given feedstock may be processed prior to use in the I2FE processes.As suggested in FIG. 6, the feedstock may first be processed to enhancethe feedstock as an LCP Feed. One purpose of such a pretreatment is tohave an increased proportion of heavier, low-octane, paraffinconstituents in the LCP Feed.

FIG. 6 shows the optional use of thermal separation of the reformate toisolate the long-chain n-paraffins for feed to the I2FE Process. Thisprovides a more limited volume feed stream for processing. The lighterboiling reformate components are already a satisfactory gasolineblendstock.

A specific boiling range can be established based upon target points tomaximize the impact of the octane gain based upon the reformatecomposition. For example, one embodiment may target a reformate cutabove 95° C. (i.e., to isolate C7 n-paraffins and higher) while anotherembodiment may target reformate above 115° C. (i.e., isolating C8n-paraffins and higher, but excluding any C8 trimethyl-pentanes and allC7 paraffins and lower) with a different yield profile and octaneresult. Yet another embodiment may target reformate above 140° C. (i.e.,to exclude all C8 paraffins and lower). These optional approaches,applicable to any LCP feed stream, reduce the overall volume of thefeedstock to be processed by enhancing the proportion of the high-chainn-paraffins in the feed stream.

In another example, a particular light Cat-Cracked Gasoline stream maypossess high olefin content and also, for example, 20% of C8 to C13n-paraffinic constituents. The hard cut to extract only the 20%n-paraffinic portion for cracking reduces the capital and operatingcosts of the reactor and catalyst, as they would only need to handle 20%vs. 100% of this cat-cracked gasoline feed.

An analysis of any proposed feed stream can be undertaken to determinethe ideal cut-point temperature to minimize the production of benzenes.For example, restricting propyl-benzene in the feedstock by selectiveseparation (by limiting constituents <159° C.) prior to the C9+ crackingstep can result in substantially lower benzene levels in the effluentwhen using hydrogen and a metal-acid catalyst with minimal impact onoctane.

In the alternative, if the entire reformate stream is to be processed,the reactor operating conditions (e.g., temperature, pressure, spacevelocity, etc.) can be established in the reforming process toselectively target the decomposition of the heaviest compounds withoutimpacting the lighter paraffin compounds that increase volume loss.

Alkyl-Aromatics

According to another embodiment of the process, other components in thefeed stream may be “selected out”. These may include certain ethyl-,propyl- or butyl-compounds by thermal slit stream or distillationmethods. The presence of methyl-aromatic compounds in the feedstock isunchanged by the I2FE reaction since methyl-benzenes do not dealkylatewith hydrogen. However, the presence of isolated ethyl-, propyl-, and/orbutyl-benzenes in reaction with hydrogen (in the absence of anymethyl-groups) may result in the production of benzene molecules plusthe off-gassing of ethane, propane or butane, respectively. Suchdistillation or slit stream processing can also be used to preventpropyl-benzene from being dealkylated—thereby reducing the creation ofbenzene in the effluent. The absence of hydrogen in the process willalso reduce the creation of benzene in the effluent.

Catalysts

The I2FE Processes disclosed herein utilize catalysts that increaseoctane and, maximize product yield. The catalysts are highly efficientat cracking long-chain paraffin molecules (particularly C10, C9 and C8paraffins) without significant degradation during the lifecycle of thecatalyst. The catalyst used in the I2FE Process generally contains astrongly acidic zeolite, with a high surface area support, for example,alumina. Additionally, there is a weakly active hydrogenation metal, forexample Molybdenum oxide, which saturates cracked olefins withoutsaturation of aromatic compounds. See Table 11.

TABLE 11 Process Options for I2FE Catalysts Zeolite I2FE CrackingReaction Catalyst w/ H2 No H2 w/ Metal Paraffin production w/ Paraffinproduction w/ minimal coking¹ olefins & coking² No Metal Olefinproduction w/ coking Olefin production w/ & excess H2 maximum coking³¹Addition of metal-impregnated catalyst with H2 saturates crackedolefins without saturation of aromatic compounds ¹Addition ofmetal-impregnated catalyst with H2 also reduces coking and simplifiesreactor design ^(2,3)Multi-bed reactor design option will address cokingand eliminate need for on-purpose hydrogen (i.e. H2 not required for theI2FE reaction)

As shown in Table 11, both the use of a metal-impregnated catalyst andthe use of on-purpose hydrogen impacts the product yield and the effecton the catalyst. A Zeolite catalyst comprising a metal-impregnatedcatalyst used in the process in the presence of hydrogen will provideparaffins (without olefins) with minimal coking. Various metals areknown to support metal-based hydrogenation, including platinum,palladium, rhenium, ruthenium, nickel, molybdenum, cobalt and copperchromium oxide. A molybdenum-impregnated catalyst is an example of acatalyst that is not overly harsh and therefore is less prone tosaturate aromatic molecules. The use of a metal-impregnated catalystwithout added hydrogen produces paraffins and olefins, along with someamount of coking.

The use of a catalyst without metal-impregnation, along with addedhydrogen, produces paraffins with olefins and with coking and excesshydrogen. A catalyst without-impregnation used without the presence ofhydrogen will result in the production of paraffins and olefins withmaximum coking, as the coking is not controlled without themetal-impregnated catalyst. The use of multi-stage reactors is anotheroption that can be utilized to minimize coking.

Traditional catalytic naphtha reforming technology uses catalysts thatcontain platinum (Pt) on chloride alumina, often promoted with eithertin (Sn) or rhenium (Re) for better yield and stability, respectively.These reforming catalysts are compositionally very different from theI2FE catalysts.

The I2FE Process uses catalysts which are functional to substantiallycrack the LCPs in the feed stream, while not significantly affectingother components of value in the feedstream. A catalyst is functional tosubstantially crack the LCPs if it cracks at least 30 wt % of the LCPs,preferably at least 50 wt %, and more preferably at least 75 wt % of theLCPs.

Other components of value may include certain C7+ aromatics known to beuseful gasoline components. C5-7 paraffins in the feedstock aregenerally acceptable in gasoline blends and they constitute componentsof value that preferably are not cracked as that may reduce the volumeof liquid product. As used herein, the term “component of value” is usedto refer to C5-C12 alkanes and alkenes; C7-C12 aromatics. A component ofvalue is not “significantly affected” if the −cracking does not reactmore than 10 wt % of the component, preferably not more than 5 wt %, andmore preferably not more than 2 wt % of the component(s) of value. Byway of example, a suitable catalyst for the disclosed processes is onewhich would crack more than 60 wt % of the C8+ n-paraffins in the feedstream but would not react more than 5 wt % of the C5-7 n-paraffins inthe feed stream.

In one embodiment, the I2FE Process is performed using a zeolitecatalyst. The acidic sites in zeolite catalyze cracking reactions ofC8-13 paraffinic compounds more rapidly than other components. Thezeolite may also catalyze other cracking reactions, but more slowly. Thereactions can be conducted both with and without metal impregnation. Themetal allows hydrogen, if present, to add across olefinic compounds thatare produced during the cracking mechanism. Not using a metal increasescoking of the reactor since olefins will react to create many differentheavy compounds.

In one aspect, the processes use a zeolite catalyst having a pore sizeof 3 to 8 Angstroms. Exemplary surface areas for the catalyst are 400 to800 m2/gram. Examples of the zeolite catalysts include Si, Al and O,preferably with an Si:Al ratio of 10 to 300. Zeolite catalysts withproperties outside of these limitations may also be useful. The catalystis preferably selected to substantially catalyze the LCPs while notsignificantly affecting the other components of value in the feedstream.

In embodiments, the catalyst is Zeolite ZSM-5, Zeolite Beta or ZeoliteMordenite. Impregnation of these catalysts all use the same metal atvarying concentrations for activity. Aluminum heptamolybdate is oneexample of a metal used to impregnate the zeolite catalyst withmolybdenum. This creates a bifunctional catalyst that is an acid andmetal. Zeolites are characterized via the following ways: pore size—3 to8 angstroms usually; pore structure—many types; and chemicalstructure—combination of Si, Al, and O. All have ammonium cations(except one version of mordenite) until impregnation and all have molarSi/Al ratios of 10 to 300.

Zeolite Beta has the following properties: 5.5-7 angstroms pore size,SiO2 to Al2O3 molar ratio (Si/Al) ranging from 20 to 50, intergrowth ofpolymorph A and B structures, and surface area between 600 and 800m2/gram.

Zeolite Mordenite has the following properties: 6-7 angstroms pore size,sodium and ammonium nominal cation forms, Si/Al ratio of 10 to 30, andsurface area between 400 and 600 m2/gram.

In a particular embodiment, the catalyst is Zeolite ZSM-5. ZSM-5 has thefollowing properties: 5-6 angstroms pore size, pentasil geometry forming10-ring-hole configuration, Si/Al ratio of 20 to 280, and surface areabetween 400 and 500 m2/gram. Various impregnations can and have beenconducted between 1% and 2% molybdenum. ZSM-5 has the ability topreserve chemical composition of the aromatic compounds in the reformatefeedstock by minimizing transalkyation. The reaction can be conductedboth with and without metal impregnation. The metal allows hydrogen toadd across olefinic compounds that are produced during the crackingmechanism. Not using a metal increases coking of the reactor sinceolefins will react to create many different heavy compounds. The smallerpore size of the ZSM-5 catalyst resulted in far less cracking andtransalkylation of aromatic compounds, which are a key part of thereformate stream. The long-chain n-paraffin compounds reacted morefavorably to the ZSM-5 structure without disturbing the aromaticcompounds.

Zeolite Catalyst Example

In one embodiment, this invention processed an entire reformate streamusing a zeolite ZSM-5 catalyst using (1-2% molybdenum) with an operatingtemperature of 250° C., a pressure of 100 psi, and a WHSV from 1.5 to3.0. Long-chain paraffins (C8+) with low-octane values were selectivelytargeted by the tailored operating conditions and were transformed tohigher octane constituents for gasoline blending and hydrogen recovery.As shown in Table 12 and FIG. 7, the aromatics in the feed stream werepreserved to a substantial extent using the ZSM-5 catalyst.

TABLE 12 ZSM-5 Preserved Aromatics vs. Beta and Mordenite (% Wt) ZSM-5,1% Mo Beta, 1% Mo Mordenite, 1% Mo 1.5 WHSV, h⁻¹ 71.24 45.58 43.62 3.0WHSV, h⁻² 80.14 61.11 62.85

As shown below in Table 13, the LCPs with low octane were reduced by 31%and the C5-C7 and lower paraffins (with improved octane, e.g.isopentane, isobutane, etc.) increased by 24%. Heavier olefins andnaphthenes were also reduced. Overall, the Octane Value increased 6%,the (pre-blending) benzene level was below 1%, and net volume loss was5%.

TABLE 13 Wt % Key Compounds Reformate Reactor Effluent Delta (%)Paraffins ≤C7 16.59 20.61 24.2% Paraffins ≥C8 13.54 9.3 −31.3%Naphthenes ≤C7 1.48 1.49 0.7% Naphthenes ≥C8 0.62 0.57 −8.1% Olefins ≤C70.59 0.43 −27.1% Olefins ≥C8 0.45 0.12 −73.3% Aromatics 66.52 66.89 0.6%

Contaminates

The cat-cracked liquid effluent may contain contaminates which call forspecialized treatment methods and/or conditions. For example, the C8 toC13 streams of CCG often contain a proportion of sulfur compared totheir neighboring C6 to C7 liquid streams, typically up to 100+ ppm. Inone embodiment, the I2FE Process applied to the CCG feed uses a metalcatalyst compatible to effectively treat and remove sulfur (50 ppm)while also hydrocracking the long-chain n-paraffins. The choice ofcatalysts for processing CCG requires sensitivity to treating the sulfurwithout damaging the catalyst.

If processing streams containing sulfur, this invention uses similarzeolite catalysts with a different hydrogenation metal, typicallyCobalt-Molybdenum Sulfide, which saturates cracked olefins withoutsaturation of aromatic compounds, while producing hydrogen sulfide (H2S)for extraction. The preferred embodiments of this reaction utilize aZeolite catalyst (Beta, Zsm-5, Mordenite, Y-zeolite-Faujasite) withMolybdenum-Sulfide or Cobalt-Molybdenum-Sulfide with alumina as a bindersupport. This catalyst hydrocracks the paraffins and creates H2S,thereby largely removing sulfur from the effluent stream which can thenbe subsequently blended into the gasoline stream. The embodiment thuscombines the hydrotreating (to eliminate sulfur) with hydrocracking in asingle step to selectively eliminate the formation of paraffins thattend to have lower octane levels.

The result is an enhanced hydrocarbon stream with a higher-octane valueand much lower sulfur content with minimum yield loss for improvedgasoline blending. This is distinctly different than traditionalhydrotreating methods as it is focused solely on production ofhigh-octane, low-sulfur gasoline blendstocks. This is unique andextremely valuable to the gasoline blending business.

Operating Conditions

The use of the selective I2FE Processes requires the operatingconditions to be at uncharacteristically low temperatures and pressuresfor hydrocracking, to thereby selectively crack the targeted molecules,e.g., C8-13 n-paraffins. This enhances the impact to increase the octanelevel of the hydrocarbon stream.

Operating conditions for the preferred embodiment of the gas-phasehydrocracking reaction are temperatures ranging from the bubble point ofthe feed stream up to 370° C., pressure of 50-250 psi, and weight hourlyspace velocity (WHSV) of 0.5 to 10. Select scenarios may call forconditions that vary from these amounts.

Products Fuel Blendstocks

The result of the cracking reactions is a higher-octane C5+ liquid phaseand a gas phase. The liquid phase effluent typically has a higher yieldat lower severity levels than its upstream feed source. It has higheroctane values due to the reduction of the octane drag from crackinglow-octane, long-chain paraffins into liquid and gas constituents. Inone embodiment, the severity level of the upstream catalytic reformerunit is reduced to result in higher liquid yields, offering the processto be utilized to crack a larger portion of long-chain paraffins at alower cost due to its lower operating temperature and pressure of theprocess. These liquid hydrocarbon compounds may be used directly in thegasoline blending process.

Typically, gasoline blending in a refinery is the complex integration ofas many as 5 to 15 processing streams into the gasoline blending center.These streams may include for example, cat-cracked gasoline (primarilyolefins), reformate (primarily aromatics, paraffins), alkylate(iso-paraffins), C4/C5 Isomerate (used for RVP), straight run gasoline(light naphtha), and various specialized distillation cuts to improvefuel performance properties.

The goal of I2FE is to enhance the octane performance of the reformatestream by reducing the n-paraffin content while preserving the aromaticcontent. Therefore, the product of I2FE is in range of high-octanegasoline components, as an enhanced reformate blendstock, primarilycomprised of aromatics, branched and cyclo-paraffins and some olefinsall ranging from C4 to C13. Due to the blending and regulatorycomplexity of light C4 and C5 compounds used for increasing vaporpressure of the final gasoline, it is often desirable to reduce theamount C4 and/or C5 present in the I2FE effluent, as these paraffins andiso-paraffins are typically added at the time of final fuel blending.

Light Gases

The gas phase compounds may be handled in various ways. In oneembodiment, the gas phase compounds are rerouted for industrial fuel useor are recycled (including hydrogen) to an upstream process unit (e.g.,catalytic reformer). In one embodiment, some C5and C6 straight chaincompounds are subsequently isomerized using existing refinery technologyand are used for gasoline RVP blending requirements.

Diesel Fuel Controlling Benzenes

Benzene content is limited in gasoline blendstocks. Since there aregasoline specifications which set limits on its use, it becomesimportant to manage benzene levels in the effluent or have a separatebenzene offtake for petrochemical use. One feature of this invention isthe ability for the process to limit the amount of benzene in theprocessed effluent using selective separation methods.

Table 14 provides a listing of various alkyl-aromatics. In the absenceof methyl groups, such alkyl-aromatics could react with hydrogen toyield benzene.

TABLE 14 Alkyl-Aromatics Aromatic Compund Formula Boiling Point ° C.ETHYLBENZENE C8H10 136.2 P-XYLENE C8H10 138.4 M-XYLENE C8H10 139.1O-XYLENE C8H10 144.4 ISOPROPYLBENZENE C9H12 152.4 N-PROPYLBENZENE C9H12159.2 M-ETHYLTOLUENE C9H12 161.3 P-ETHYLTOLUENE C9H12 162.01,3,5-TRIMETHYLBENZENE C9H12 164.7 O-ETHYLTOLUENE C9H12 165.2TERT-BUTYLBENZENE C10H14 169.1 1,2,4-TRIMETHYLBENZENE C9H12 169.4ISOBUTYLBENZENE C10H14 172.8 SEC-BUTYLBENZENE C10H14 173.3 M-CYMENEC10H14 175.1 1,2,3-TRIMETHYLBENZENE C9H12 176.1 P-CYNENE C10H14 177.1O-CYMENE C10H14 178.2 M-DIETHYLBENZENE C10H14 181.11-METHYL-3-N-PROPYLBENZENE C10H14 182.0 N-BUTYLBENZENE C10H14 183.31-METMYL-4-N-PROPYLBENZENE C10H14 183.4 O-DIETHYLBENZENE C10H14 183.41,3-DIMETHYL-5-ETHYLBENZENE C10H14 183.6 P-DIETHYLBENZENE C10H14 183.81-METHYL-2-N-PROPYLBENZENE C10H14 184.9 1,4-DIMETHYL-2-ETHYLBENZENEC10H14 186.8 1,3-DIMETHYL-4-ETHYLBENZENE C10H14 188.21,2-DIMETHYL-4-ETHYLBENZENE C10H14 189.5 1,3-DIMETHYL-2-ETHYLBENZENEC10H14 190.1 1,2-DIMETHYL-3-ETHYLBENZENE C10H14 193.91,2,4,5-TETRAMETHYLBENZENE C10H14 196.8 1,2,3,5-TETRAMETHYLBENZENEC10H14 198.0

Operating Conditions

In another aspect, the I2FE operating conditions can be varied in such away as to selectively minimize any production of benzene (withoutthermal separation as a precursor) by altering the process temperature,pressure and WHSV to ideal conditions for minimizing benzene. FIG. 8shows the benzene reduction in comparison to I2FE reactor temperature.

In embodiments, various processing steps may be combined to reduce theproduction of benzene. For example, selective thermal separationscombined with specialized operating conditions can work together tominimize the production of benzene.

In some cases, a benzene thermal separation step may be cost-effectivein preparing benzene for downstream BTX operations. In a relatedembodiment, separating C6-C9 alkyl-aromatics and conducting ahydrodealkylation processing step can further prepare BTX compounds forsuch petrochemical processing. Hydrodealkylation can eliminateundesirable close boiling aromatic compounds and streamline the BTXpetrochemical pre-treatment process. In other cases, the absence ofhydrogen in the I2FE process can restrict the conversion ofalky-aromatics to benzene, thereby optimizing the process to yield highoctane gasoline blendstocks with controlled amounts of benzene, yetbelow regulatory levels for the final blended gasoline.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same is to be considered asillustrative and not restrictive in character, it being understood thatonly the preferred embodiment has been shown and described and that allchanges, equivalents, and modifications that come within the spirit ofthe inventions defined by following claims are desired to be protected.

1. A method for making a higher-octane fuel component from a feed streamcontaining C8+ paraffins, comprising: catalytically cracking C8+paraffins in the feed stream using a Zeolite catalyst under operatingconditions suitable to substantially convert the C8+ paraffins to areaction product comprising mid-chain paraffins and olefins andshort-chain paraffins and olefins converted from the C8+ paraffins, thereaction product comprising a liquid phase containing product mid-chainparaffins and a gas phase containing product short-chain paraffins; theliquid phase paraffins having an Octane Value that is at least 1 OctaneValue higher than the Octane Value of the paraffins in the feed stream;and separating the liquid phase from the gas phase.
 2. The method ofclaim 1 in which the catalyst is a hydrogenation-metal-impregnatedcatalyst converting the olefins to paraffins.
 3. The method of claim 1in which the liquid phase further comprises C8+ paraffins.
 4. The methodof claim 3 and which further includes using the liquid phase as a fuelcomponent.
 5. The method of claim 4 in which the feed stream includesC5-13 n-paraffins, the method further comprising separating out aportion of the C5-13 n-paraffins are separated out for use as a fuelcomponent.
 6. The method of claim 1 in which the operating conditionsinclude a temperature below about 370° C., a pressure below about 250psig, and a flow rate of about 1.5 to about 3 WHSV.
 7. The method ofclaim 6 in which the C8+ paraffins comprise C8-13 paraffins.
 8. Themethod of claim 7 in which the C8+ paraffins comprise C8-13 n-paraffins.9. The method of claim 8 in which the catalytic cracking is performedunder conditions to substantially crack the C8-13 n-paraffins.
 10. Themethod of claim 9 in which the feed stream further includes aliphaticand/or aromatic hydrocarbons.
 11. The method of claim 10 in which thefeed stream includes aromatics and the catalytic cracking is performedunder operating conditions in which less than 5% of the aromatics aresaturated.
 12. The method of claim 6 in which the feed stream comprisesan output stream downstream of a catalytic reformer or a catalyticcracker.
 13. The method of claim 12 in which the feed stream comprises acomplete reformate stream.
 14. The method of claim 12 which furtherincludes addition of hydrogen to the feed stream prior to the catalyticcracking.
 15. The method of claim 14 in which the catalyst is ahydrogenation-metal-impregnated catalyst converting the olefins toparaffins.
 16. The method of claim 12 in which the catalytic cracking isperformed without hydrogen other than that present in the output streamto reduce conversion of alkyl-aromatics to benzene and/or reduce coking.17. The method of claim 12 which further comprises pretreating the feedstream (e.g. reformate, CCG) prior to catalytic cracking, thepretreating being selected from the group consisting of thermalseparation, slit stream, distillation and sulfur-reduction.
 18. Themethod of claim 17 in which the pretreating is selected from the groupconsisting of thermal separation to provide a feed stream cut at anytargeted point including above 95° C., thermal separation to provide afeedstream cut above 115° C., thermal separation to provide a feedstreamcut above 140° C. , thermal separation to provide a feedstream cut above159° C.
 19. A method for making a higher-octane fuel component from afeed stream containing C8+ paraffins, comprising: catalytically crackingC8+ paraffins in the feed stream using a catalyst and operatingconditions suitable to substantially convert the C8+ paraffins to areaction product comprising product mid-chain paraffins and productshort-chain paraffins converted from the C8+ paraffins, the paraffinsbeing converted in a two-step process in which the paraffins are firstconverted to a combination of short-chain paraffins and short-chainolefins, and the olefins are then hydrogenated in the presence of ametal-impregnated catalyst to form mid-chain paraffins, the reactionproduct comprising a liquid phase containing product mid-chain paraffinsand a gas phase containing product short-chain paraffins; the liquidphase effluent having an Octane Value that is at least 1 Octane Valuehigher than the Octane Value of the feed stream; and separating theliquid phase from the gas phase.
 20. The method of claim 19 in which theOctane Value of the liquid phase effluent is at least 3 more than theOctane Value of the feed stream.
 21. The method of claim 20 whichfurther includes addition of hydrogen to the feed stream prior to thecatalytic cracking.
 22. The method of claim 21 in which the C8+paraffins comprise C8-13 n-paraffins, and the catalytic cracking isperformed under conditions to substantially crack the C8-13 n-paraffins.